Push bench method and apparatus



May 11, 1937. 5. SMITH PUSH BENCH METHOD AND APPARATUS Filed Sept. 25, 1935 bregmfir, WQQWA Patented May 11, 1937 *PATE NT FFICE 2,080,344 PUSHBENGH' M'ETHOD AND APPARATUS Sydney Smith, London, England, assignor to Wellman SeaverRolling Mill CompanyLimited, London, Eng-land, a company or Great Britain Application September 25, 1935, Seria-INo. 42,105 In Great. Britain October 23, 1934 Claims.

This invention relates toia'method of and 'apparatus for the manufacture of metal tubes. and other tubular metal articles.

The apparatus is of the push bench type by 5 "which a somewhat thick'cup-shaped hollow billet carried on an end of a mandrel is pushed through diesv or through passes between rolls which decrease successively in cross-sectional area in the forward direction, whereby the billet is reduced inthickness and spread out lengthwise along the mandrel until the billet is brought to or approximately to the'form of a tube of the required thickness and length. An example of such apparatus is described in the specification of British Letters Patent No. 300,288.

It has been proposed to produce a gun tube by piercing a central hole in a cast steel billet while the latter is supported externally and then to submit the hollow blank, having one end closed, to successive drawing operations by forcing it through sets of draw dies of successively decreasing diameter by successive mandrels each of materially smaller diameter than the internal diameter of the extruded blank and partly formed tube, the blank being re-heated before each drawing operation. The blank is thus free to contract in diameter internally and the external and internal diameters are reduced simultaneously with elongation of the tube as a whole. With a method 30 of this kind, in order to prevent each drawing mandrel pushing through the closed end of the blank or partly formed tube, it is necessary to cool the closed end, as by spraying it with water, prior to a drawing operation. It is found that as the result of using a smaller mandrel for a successive drawing operation difficulties are experienced in that waves and unevennesses are produced in the metal, and a surface wave, once produced, cannot be removed by subsequent drawing operations. At the same time the concentricity of the tube is not true and truing operations have to be performed between drawing operations.

The object of the present invention is to provide greater accuracy in the concentricity of the tube with a more even thickness, to improve the texture of the metal of the finished tube, to render possible the production of long light tubes by push bench apparatuses and to increase the speed of production. It has been discovered that such objects may be attained if the drawing operation is carried out in two or more steps in a plurality of push benches with the speed of drawing increasing in the successive benches with, in some cases, a re-heating of the article prior to intro duction into a successive bench.

According to. the present invention therefore a method of manufacturing metaltubes and other tubular metal articles consists in treating a'some what thick'cup-shaped hollow billet carried on the ,end of amandrel in a first push bench drawing apparatus, then transferring the'tubular article produced thereby to a second push bench drawing apparatus and treating it again at a greater drawing speed. In some cases thehollow billet may be treated in a heating furnace priortotreatment in the second push bench apparatus.

The "tubular article .may be .transferred to a successive push bench apparatus while stillon the mandrel and the operation in the successive ap paratus is carried outwith the tubular article on i the same mandrel. Onthe otherhand; particularly when the article is treated ina heating furnace, it may be stripped from its mandrel prior to re-heating and placed on another mandrel of substantially the same diameter as the first mandrel for the successive treatment.

The invention will now be described by way of example with reference to the accompanying drawing which is a diagrammatic plan view partly in section of apparatus embodying two push benches arranged side by side.

A first push bench apparatus A has a driving rack I, a mandrel carrier 2, a mandrel 3 and dies 4 which decrease successively in cross-sectional area, and which are mounted in a ring bed 5. Beyond and in line with the push bench A is a stripper 6 by which the tube is removed from the mandrel 3. The stripper may be of any known and convenient form and in the present case comprises a pair of gripping jaws l which engage a depression in the mandrel and hold it while a slotted plate 8 placed at the back of the tube H and attached by rods 9 to hydraulic apparatus I0 is drawn forward by the latter to remove the tube from the mandrel. I2 is a table from which the tubes are fed to a heating furnace l3 while the mandrels are delivered to a runway l6 and returned to the push bench. From the furnace l3 the tubes are removed by pusher means IT to a table indicated at M which feeds them in front of the mandrel of a second push bench drawing apparatus B wherein I is the driving rack, 2' the mandrel carrier, 3 the mandrel and 4 the dies mounted in the ring bed 5'.

In use a somewhat thick cup-shaped hollow billet I5 is delivered in front of the mandrel 3 of the first push bench apparatus A. The mandrel 3 is advanced to enter the billet and push it through the dies 4' whereby it is reduced in thickness and spread out lengthwise along the mandrel in the form of a tube II. The tube is then removed from the mandrel by the stripper and delivered to the heating furnace I3 where its temperature is increased or evened up. After removal from the furnace the tube may be treated to remove any internal scale, for example it may be tipped up at the closed end and tapped. It is then delivered by the table H5 in front of the mandrel 3 of the second drawing apparatus B, said mandrel being of the same diameter as that of the first drawing apparatus. The mandrel is advanced to enter the tube II and push it through the dies 4' at a greater speed than that at which it was pushed through the dies 4 of the first apparatus whereby it is spread out still further along the mandrel and its thickness is further reduced. The tube is subsequently stripped from the mandrel.

By performing the first drawing operation at a lower speed than a successive drawing operation the peak load on the driving means of the whole apparatus is lower but the output of tubular articles, due to operating on the work on two or more push benches, is increased. Further greater accuracy in the concentricity of the tubes and improved texture of the metal in the finished tube is obtained, so that it is possible to produce longer and thinner tubes than when a single push bench is employed.

Re-heating of the tubular articles between the drawing operations performed on successive benches is desirable when long light tubes are produced.

What I claim is:

1. A method of manufacturing metal tubes and other tubular metal articles consisting in reducing a somewhat thick cup-shaped hollow billet carried on the end of a mandrel in a first push bench drawing apparatus then transferring the tubular article produced thereby to a second push bench drawing apparatus and reducing it again at a greater drawing speed.

2. A method of manufacturing metal tubes and other tubular metal articles according to claim 1 wherein the tubular article produced in the first push bench drawing apparatus is treated in the second push bench drawing apparatus while carried on the same mandrel.

3. A method of manufacturing metal tubes and other tubular articles according to claim 1 wherein the tubular article produced by the first push bench drawing apparatus is stripped from its mandrel, re-heated and placed on a mandrel of substantially the same diameter as the mandrel used in the first push bench operation for treatmerit in thesecond push bench apparatus.

4. A method of manufacturing metal tubes and other tubular metal articles according'to claim 1 wherein the tubular article produced by the first push-bench apparatus is stripped from its mandrel, reheated, and treated to remove internal scale, before being reduced in the second push-bench apparatus.

5. Apparatus for manufacturing metal tubes and other tubular metal articles comprising two push bench apparatuses arranged side by-side, stripper means in line with the first push-bench apparatus, and a heating furnace at the side of the stripper means and between the two push bench apparatuses, to receive the tubular article from the first push bench apparatus prior to its delivery to the second push bench apparatus.

SYDNEY SMITH. 

